1. Field of Invention
The present invention relates to radar video display and recording devices and, more specifically, to a radar video display and recording device that utilizes a radar video capture card on a personal computer platform to simultaneously display the whole and designated areas in the polar coordinates and Cartesian coordinates, respectively.
2. Related Art
Referring to FIG. 1, which shows a conventional radar system block diagram. The system includes a pulse generator 11, a modulator 12, a receiver 13, a video signal processor 14, a transmitter 15, a duplexer 16, an antenna 17, and a scope 18.
First, the pulse generator 11 produces and transmits a trigger signal T to the modulator 12, the receiver 13, and the video signal processor 14. After receiving the trigger signal T the modulator 12 converts it into a pulse P and sends it to the transmitter 15 for transmission. The duplexer 16 couples a microwave signal M transmitted by the transmitter 15 to the antenna 17 and couples a radar return echo E received by the antenna 17 to the receiver 13. The receiver 13 converts the radar return echo E into an original video signal V. The video signal processor 14 then performs preprocessing on the original video signal V to eliminate noises and clutters contained therein and to convert analog original video signal V into a digital video signal D. Finally, the scope 18 makes the digital video signal D into a visible image.
In particular, the scope 18 has many ways of displaying. The most common one is the P-scope, or plan position indicator (PPI) as shown in FIG. 2. A rotational beam B is provided on the scope 18 and synchronously rotates with the antenna 17. When the radar return echo E is received by the antenna 17, it is then converted into the digital video signal D according to the above method and displayed on the scope 18 in the form of a bright spot S to show the relative position of the detected object. For radar examination equipment and some special radar devices, they often need another style of display, namely, the B-scope as shown in FIG. 3. The horizontal and vertical axes in the drawing represent the azimuthal angle and range, respectively.
However, the P-scope only displays single channel radar videos in the polar format. This display style has overlapped bright spots S for objects within a short distance adjacent to the transmission direction, which results in influential effects on the originality of the digital video signal D. Although the B-scope displays images in the rectangular format so that bright spots S adjacent to the transmission direction would not overlap and the image originality can be kept in the digital video signals, they are still single channel ones. Furthermore, the displayed range is so small that the whole area can not be shown.
Besides, when the video signal processor 14 performs preprocessing on the original video signal V to eliminate noises and clutters contained therein, the choice and design of algorithms depend upon the noise and clutter distributions. They are not only different by times and places, but receive more significant influences from weather changes. Therefore, subsequent signal analysis and algorithm verification are necessary. Nevertheless, the conventional P-scope or B-scope only displays single channel radar video signals and cannot simultaneously show the radar video signals of the whole and designated areas, the function provided thereby is so simple that subsequent signal analysis and algorithm verification become more tedious and time-consuming.
Currently, there are many patents or products in the United States of America that aim at solving the above problems. For example, the U.S. Pat. No. 3,634,887 and Pat. No. 3,840,874 proposed one type of recording and displaying device for radar video signals that can mix and store the digital video signals D and trigger signals T in a video tape for subsequent signal analysis and algorithm verification. The radar storage conversion system invented by Folsom Research, Inc. can provide both P-scope and B-scope display formats at the same time. It can also convert the digital video signals D of the two display formats into the RS-170A format and store them in a video tape for subsequent signal analysis and algorithm verification. With reference to FIG. 4, the U.S. Pat. No. 4,729,029 proposed a method for magnifying an inset on the scope 18 and displaying the magnified image on the same scope by providing an overlapped window W.
In spite the fact that the U.S. patents and products mentioned hereinbefore make some improvements in the problems that current P-scopes or B-scopes can only display signal channel radar videos and are unable to simultaneously display the radar video signals of the whole and designated areas, the methods proposed by the U.S. Pat. Nos. 3,634,887 and 3,840,874 would have distortion on the stored digital video signals D and trigger signals T due to the narrow frequency band of the video tapes. The method proposed by the U.S. Pat. No. 4,729,029 can simultaneously display radar video signals of the whole area and designated inset I magnified, but the magnified digital video signals D are displayed in the polar format. As mentioned above, this display style has overlapped bright spots S for objects within a short distance adjacent to the transmission direction, which damages the originality of the digital video signal D.
In view of the foregoing, it is a primary object of the present invention to provide a radar video display and recording device which can simultaneously display radar video signals of the whole and arbitrarily designated areas and store the signals of designated areas into a recording media (such as a hard disk drive) so as to obtain a long-time continuous radar video information of the designated areas for subsequent analysis and algorithm verification. In addition, the present invention can simultaneously display radar video signals at different processing stages in the video signal processor on a scope for the convenience of observing the work condition at each signal processing stage. Since two windows are utilized to display the radar video signals of the whole area and the designated area on a scope, and they are displayed in the polar and rectangular formats, respectively, the present invention can simultaneously solve the problems of displaying radar video signals of the whole and designated areas and of keeping the originality of radar video signals that cannot be done at the same time using the prior art.
To achieve the above goal, the present invention utilizes a radar video capture unit to analyze and store radar video signals of the whole and designated areas and to have the video signals at different processing stages in the digital video processing unit displayed on one scope for observing the work condition at each processing stage.